Today a small band of residents opposed to Sunoco’s multi-billion dollar plan to transport volatile gases through their densely populated neighborhoods will take their case directly to the state Public Utility Commission.

Nothing else has stopped Sunoco and parent company Energy Transfer Partners out of Texas from pushing toward the date when they will push the button to begin moving hundreds of thousands of barrels of butane, ethane and propane from the state’s Marcellus Shale regions across the full width of Pennsylvania to a facility in the former refinery at Marcus Hook.

Once there it will be stored and shipped – for the most part to foreign customers.

The group of citizens from Chester and Delaware counties not only want the PUC to block Sunoco from putting Mariner East 2 online, they want the state agency to halt the same materials that are already flowing through a smaller, existing pipeline.

Sunoco wants to puts its Mariner East 2 pipeline, which has struggled with a series of delays, in operation by the end of the year. But they have been unable to complete the project with newly installed 20-inch pipe. So they are planning to use older, existing 16- and 12-inch pipe to fill in the gaps.

Residents, who have not exactly been enamored with having this new pipeline as a neighbor, sometimes in their backyards and within a couple of hundred feet of schools and senior centers, believe the plan only increases what they already see as a risky plan.

Specifically, they claim Sunoco has not provided the public with a credible public awareness program in the event of a leak of these volatile natural gas liquids.

More than that, they also are asking the PUC to permanently halt operation of the pipelines, saying the project runs afoul of state laws regulating safe operation of utilities. They make the argument that the PUC has an obligation to protect citizens by ensuring pipeline safety.

It’s not the first time the argument has been made.

For months residents have complained to anyone who would listen – local governing bodies, county council, state legislators, Gov. Tom Wolf, and the PUC – asking them to intervene and halt the project.

So far their arguments have fallen on deaf ears.

For their part, Sunoco insists the state already has verified the safety of both the Mariner East 1 and 2 pipelines. They point out they have adhered to all PUC mandates, including several that stopped work on the line for months and delayed completion of the pipeline.

The company also says they have worked closely with local authorities and have actively made their Public Awareness Program available to the public through a series of mailed brochures, face-to-face liaison meetings and specialized training.

They say the 12-inch line that will be used to fill in some spots on Mariner East 2 underwent a $30 million upgrade in 2016.

Now Sunoco is pushing to get Mariner East 2 online.

A risk analysis paid for by a grassroots group opposed to the pipeline underscored the concerns that have been raised by pipeline foes for months.

Specifically, it warned that in the case of a leak of hazardous, highly volatile liquids for the proposed 20-inch pipeline could extend up to 2,135 feet away from the site of the leak or rupture.

That reinforces one of the loudest complaints of pipeline foes, who question the notion of sending such volatile liquids through densely populated neighborhoods here in Delaware and Chester counties.

Today’s hearing might just be the last stand for residents opposed to Mariner East 2.

Mariner East 2 will run approximately 23 miles across the heart of Chester County before hitting the Delaware County border. Then it will snake another 11 miles across the western end of the county before arriving in Marcus Hook, following roughly the same path of the old refinery pipeline that carried petroleum to the refinery for years.

But today the Battle of Mariner East 2 will take a detour to the state capital.

Opponents will make their case before the PUC. They will argue that this is a terrible idea and that Sunoco’s new “hybrid” plan to get the pipeline up and running only makes things worse.

It’s an uphill battle, one that they have made before.

Back in May, state Sen. Andy Dinniman used a similar petition to the PUC and got construction halted after sinkholes developed in a West Whiteland neighborhood believed connected to drilling for Mariner East 2 that exposed the old Mariner East 1 pipeline. That edict was later partially overturned by the full PUC.

Regardless of what they rule, one thing is fairly certain. State regulators – as with everyone else connected to this project – will not be able to answer the one question that continues to hang over this proposal, the one that keeps residents awake at night thinking about their new neighbor, carrying hundreds of thousands of barrels of volatile liquid gases just feet from their homes.